NEWARK — The Transportation Security Administration on Friday moved to fire 25 employees at Newark Liberty International Airport and suspend 19 others for what it said was improper screening of checked luggage, the latest in a series of sanctions at one of the country’s busiest airports.

The alleged screening failures were uncovered late last year after surveillance cameras were installed in one of the airport’s 25 screening rooms to check for possible thefts, the TSA said.

Eight employees were fired in June in the investigation. The latest action raises to 52 the number of TSA employees at Newark caught up in the investigation, making it the biggest single disciplinary action taken by the TSA at a U.S. airport.

An official of a union that represents some of the Newark employees said Friday it’s likely the union will seek to have the employees reinstated. The union has seven days to answer the TSA’s proposal.

“The charges right now seem to be improper screening of bags, which we don’t feel is correct,” said Stacy Dodtmann, regional vice president of the American Federation of Government Employees. “We feel they performed their jobs to what they were trained to do.”

The latest group cited includes screeners, as well as managers accused of failing to effectively supervise their employees. Among the allegations is that screeners failed to open up and physically check bags that had been flagged by X-ray machines.

All the screeners cited for failing to follow procedures were removed from their jobs in November and December and given non-screening duties pending completion of the investigation, the TSA said.

The TSA has more than 1,400 employees at Newark, one of the New York area’s three major airports.

“The decision to take disciplinary actions today with the proposed removal of 25 individuals and suspension of 19 others reaffirms our strong commitment to ensure the safety of the traveling public and to hold all our employees to the highest standards of conduct and accountability,” said Lisa Farbstein, a TSA spokeswoman.

The theft investigation, which the TSA said was the reason the cameras were installed, did not lead to any charges. The TSA said an employee who was a suspect in that probe ended up resigning, though the cameras were left in place, turning up the screening lapses.

The previous biggest disciplinary action taken by the TSA was last year at Honolulu International Airport, where 48 employees were proposed for firing or suspension, also for failing to properly screen luggage.

All 44 employees cited Friday have the right to appeal. The proposed suspensions would for up to 14 days, and without pay.